ZZ-CT is a 3x3 method proposed by Chris Tran. It is a variant of the ZZ Method with a unique 2 look LSLL, divided into TSLE and TTLL.

TSLE inserts the last edge whilst orienting all corners. (108 cases, all trivial) This step is 100% 2-gen and all states can be solved by a linear combination of at most three R U R', R U' R', or R U2 R' triggers, which permits simple memorization and executions. Many of the TSLE insertions are the same as the traditional F2L algorithm, and has a much lower move count than other last slot methods since it ignores permutation of the corners and edges except UF. Using RUD, LUR, and non-2gen algorithms improves upon ergonomics and move count and allows for even shorter inserts.

TTLL forces an LL Skip with only 72 cases (42 w/mirrors, 30 non-trivial). It is named after Chris Tran (creator) and Blake Thompson ( who generated a significant fraction of the algorithms)

Steps

History:

ZZ-CT was created with the intention of fixing everything wrong with ZBLL, and to create the first feasible LL-Skip method under 200 algorithms. Several months of brainstorming and evolution led to ZZ-CT.

The core fundamental concept is the orientation of corners before reaching last layer.

By abusing rotational symmetry statistics of oriented pieces, it was observed that algorithm count could be reduced by at least an order of magnitude or more. This pre-orientation also allowed for simple and obvious recognition of permutation.

The first incarnation of this method was one which oriented all corners during the completion of the third slot, and then forced LL skip (~800-1000 algorithms).

ZZ-HW was the next big improvement, which oriented all corners and inserted the corner in the fourth slot, followed by forced LL skip(~200 algorithms). However, this method was limited by algorithm ergonomics, since diagonal corner swap and edge insertion algorithms are too long and are not sufficiently ergonomic for competitive speedsolving purposes.

However, by maintaining the same concept and algorithms, but inserting an edge instead of a corner, this hindrance could be ignored, and novel beneficial attributes were serendipitously discovered, as reported herein.

Advantages:

When compared with ZBLL, ZZ-CT solves the issues of large algorithm count, recognition, statistical hindrances, practise requirement, and steep learning curve by having a significantly lower algorithm count, obvious colour blocks (PLL-style recognition), and better statistics for the same amount of looks.

TSLE is also easily recognised, and only involves looking at orientation of corners and finding the last edge.
This requires a similar mental load as OLL, and does not require knowing where the last LS corner is.

Similar to intuitive edge control in CFOP, the same concept can be used to simplify TSLE.

For example, in CFOP, intuitive edge control is seeing that there are no oriented edges and doing R F R F'(sledgehammer) instead of U R U' R'. This ensures no dot cases, reducing OLL by 7 cases.

In ZZ-CT, intuitive corner control is as simple as observing there are no oriented corners, and doing R' U2 R instead of U R' U R during third slot to avoid all misoriented corners, which reduces TSLE by 16 cases. Intuitive corner control can even force superior TSLE cases with better execution, recognition, and move count, in the same way that intuitive edge control forces a better OLL.

Lookahead into TTLL is also similar to lookahead into PLL during OLL.
Since oriented colour blocks are being put together, it is easier to predict the last algorithm. This is opposed to ZBLL, in which formation of LS brings together misoriented colour blocks, which are harder to discern for lookahead purposes.

Statistically, ZZ-CT leads to good single times due to the following attributes:

PLL occurs 20% of the time (1 out of 5 solves). Leading to a well known algorithm that most cubers already know.

True LL skip occurs 1 out of 360 solves (0.27%), as compared with 0.0064% in CFOP(1 out of 15552 solves), and 0.051% in ZZ(1 out of 1944 solves). Which means that the probability is increased by orders of magnitude.

2-Gen EVERYTHING occurs 29% of the time, which is twice as much as ZBLL (15%) and 1.8% chance with CFOP.

Individual TTLL probabilities are similar to OLL. In comparison, the statistics for ZBLL cases are profoundly lower. This means that some cases will only pop up every few days during solves, meaning that it requires much less practice to execute TTLL than ZBLL.

TSLE is skipped approximately one out of every 405 solves (0.24%), which adds another level of reduced single times.

Disadvantages:

"(ZZ-CT) sounds like a good method-- the only disadvantage is that you have to use ZZ."
-Andrew Ricci (2012 US Nationals Champion)